Fuel cell unit

ABSTRACT

A fuel cell unit is provided with a fuel cell for electric power generation, a mixing tank housing a mixture of fuel and exhaust from the fuel cell, a fuel tank housing the fuel, a pump delivering the mixture and air to the fuel cell, a casing housing the fuel cell, the pump and at least one of the fuel tank and the mixing tank and a partition partitioning an interior of the casing into a first compartment housing the fuel cell and a second compartment. The partition is provided with first, second and third flow paths. The first flow path connects the mixing tank to the fuel cell. The second flow path connects the fuel cell to the pump. The third flow path connects the pump to the mixing tank.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of and claims the benefit of priorityfrom U.S. application Ser. No. 10/811,846, filed Mar. 30, 2004, andclaims the benefit of priority from the prior Japanese PatentApplication No. 2003-098358, filed Apr. 1, 2003; the entire contents ofboth of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fuel cell unit which is compactlyconstituted.

2. Description of the Related Art

A fuel cell unit for a direct methanol fuel cell (“DMFC” hereinafter) isprovided with a fuel tank for housing methanol as fuel, a mixing tankfor forming a mixture of the methanol and water, a fuel cell stackcomposed of plural unit fuel cells, each of which is provided with acathode, an anode and a solid polymer electrolyte membrane puttherebetween, and pumps for feeding the mixture and air to the fuel cellstack and supplementary elements.

Japanese Patent Application Laid-open No. H09-171872 discloses a relatedart in which a fuel cell unit is housed in a casing for ease ofhandling.

SUMMARY OF THE INVENTION

According to the above related art, the casing houses several elementsconstituting the fuel cell unit, however, compactness thereof is notsufficient.

The present invention is intended for providing a fuel cell unit whichis compactly constituted.

According to a first aspect of the present invention, a fuel cell unitis provided with a fuel cell for electric power generation; a mixingtank housing a mixture of fuel and exhaust water from the fuel cell; afuel tank housing the fuel; a pump delivering the mixture and air to thefuel cell; a casing housing the fuel cell, the pump and at least one ofthe fuel tank and the mixing tank; and a partition partitioning aninterior of the casing into a first compartment housing the fuel celland a second compartment, the partition comprising first, second andthird flow paths, the first flow path connecting the mixing tank to thefuel cell, the second flow path connecting the fuel cell to the pump,the third flow path connecting the pump to the mixing tank.

According to a second aspect of the present invention, a fuel cell unitis provided with a fuel cell for electric power generation; a mixingtank housing a mixture of fuel and exhaust water from the fuel cell andconnected to the fuel cell; a fuel tank housing the fuel and connectedto the mixing tank; a pump connected to both the fuel cell and themixing tank, the pump negatively pressurizing the fuel cell wherebydelivery of the fuel to the mixing tank and delivery of the mixture andair to the fuel cell are done by the pump.

According to a third aspect of the present invention, a fuel cell unitis provided with a fuel cell for electric power water generation; amixing tank housing a mixture of fuel and exhaust from the fuel cell; afuel tank housing the fuel and comprising a porous body disposed alongan interior wall of the fuel tank and a flow path connecting the porousbody to the fuel cell; and a pump delivering the mixture and air to thefuel cell.

According to a fourth aspect of the present invention, a fuel cell unitis provided with a fuel cell for electric power generation; a mixingtank housing a mixture of fuel and exhaust from the fuel cell andcomprising a porous body disposed along an interior wall of the mixingtank, a cavity portion, an inflow path connecting the fuel cell to thecavity portion and an exhaust flow path connecting the cavity portion toan outside of the mixing tank; a fuel tank housing the fuel; and a pumpdelivering the fuel to the fuel cell.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of a fuel cell unit according to a firstembodiment of the present invention;

FIG. 2 is a schematic drawing of a fuel cell unit according to a secondembodiment of the present invention;

FIG. 3 is a schematic drawing of a fuel cell unit according to a thirdembodiment of the present invention;

FIG. 4 is a schematic drawing showing a packaging manner of the fuelcell unit in a casing according to a version of the present invention;

FIG. 5 is a schematic drawing showing a connection manner between amanifold and flow paths;

FIG. 6 is a schematic drawing of a constitution modified from theconstitution shown in FIG. 5;

FIG. 7 is a schematic drawing of a fuel tank according to an embodimentof the present invention;

FIG. 8 is a schematic drawing of a mixing tank according to anembodiment of the present invention;

FIG. 9 is a schematic drawing of a packaging manner of the fuel cellunit modified from the packaging manner shown in FIG. 4;

FIG. 10 is a schematic drawing of a constitution further modified fromFIG. 9;

FIG. 11A is a schematic drawing of a partition wall according to anembodiment of the present invention;

FIG. 11B is a schematic drawing of a partition wall according to amodified embodiment of the present invention; and

FIG. 11C is a schematic drawing of paired partition walls according toanother embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A constitution of a fuel cell unit 1 according to a first embodiment ofthe present invention will be described hereinafter with reference toFIG. 1.

The fuel cell unit 1 is provided with a fuel tank 3 for housing methanolas fuel, a mixing tank 5 for forming a mixture of the methanol andwater, a pump 7, a fuel cell 9 and a printed-circuit board 13. The fuelcell 9 has a stacked structure composed of plural unit fuel cells, eachof which is provided with a cathode, an anode and a solid polymerelectrolyte membrane put therebetween. The printed-circuit board 13 isprovided with a control circuit and a rechargeable battery 11 such as alithium-ion battery for a power source thereof. The whole elementsconstituting the fuel cell unit 1 are housed in a casing 15.

The fuel tank 3 is connected to a suction port of the pump 7 via a flowpath 19, which has a regulation valve 17. A discharge port of the pump 7is connected to the mixing tank 5 via a flow path 21. To the suctionport, an anode exhaust port 23 and a cathode exhaust port 25 of the fuelcell 9 are further connected.

The mixing tank 5 is provided with an exhaust flow path 27 forexhausting gas separated from a gas-liquid mixture formed from an inflowthrough the flow path 21. The flow path 27 is further provided with anopen-close valve 29, which is also controllable of flow regulation. Themixing tank 5 is connected to the fuel cell 9 via an anode supply path31 provided with a flow regulator 33, such as a needle valve or anorifice for example. The fuel cell 9 is provided with a cathode supplypath 37 having a flow regulator 36, such as a needle valve or an orificefor example, which communicates with an air inlet port 35.

When the control circuit on the printed-circuit board 13 regulates anddrives the pump 7, a negative pressure is applied to the suction port ofthe pump 7 and hence the anode and cathode exhaust ports 23 and 25 arenegatively pressurized. Thereby the mixture of the methanol and thewater in the mixing tank 5 and the air from the air inlet port 35 aresucked and supplied to the fuel cell 9.

Water and carbon dioxide generated by a cell reaction in the fuel cell9, unreacted air and methanol-water mixture and such are sucked to thesuction port of the pump 7. At the same time, the methanol housed in thefuel tank 3 is sucked thereto, however, a flow rate thereof is regulatedby the regulation valve 17. These fluids sucked by the pump 7 are fedthrough the flow path 21 into the mixing tank 5.

In the mixing tank 5, gas-liquid separation from the mixture of thefluids is done. Gas separated from the mixture is exhausted through theexhaust flow path 27 to the outside. Thereby methanol-water mixture isleft in the mixing tank 5 and supplied to the fuel cell 9 via the anodesupply path 31 in a condition that the flow regulator 33 regulates theflow rate thereof.

As will be understood from the aforementioned description, according tothe present embodiment, the supply of the fuel to the mixing tank 5 andthe supply of the mixture and the air to the fuel cell 9 arecollectively done by the pump 7 without any other pump means. Thereforethe number of the elements therein can be decreased and hence the totalconstitution of the fuel cell unit 1 can be compactly configured.

A constitution of a fuel cell unit 1 according to a second embodiment ofthe present invention will be described hereinafter with reference toFIG. 2.

As compared with the above first embodiment, in the present secondembodiment, the fuel tank 3 is connected to the anode supply path 31.Seen from a view point of the pump 3, the fuel cell 9 is disposedupstream of the pump 3 and the fuel tank 3 is further upstream thereof.Therefore, a compact supplementary pump 39 is preferably provided anddisposed on the flow path 19. Though the total constitution is largerfor that in a case where the supplementary pump 39 is provided, nearlythe same effect as the above first embodiment can be achieved.

FIG. 3 shows a third embodiment of the present invention. In the presentembodiment, the fuel tank 3 is directly connected to the mixing tank 5as compared with the above first and second embodiments. The compactsupplementary pump 39 is also preferably provided. According to thepresent embodiment, the same effect as the above second embodiment canbe achieved.

The fuel tank 3, the mixing tank 5, the pump 7, the fuel cell 9 and theother elements, all of which constitute the fuel cell unit 1 the fuelcell unit 1 according to any of the first through third embodiments, arehoused in the casing 15 as exemplarily shown in FIG. 4.

The casing 15 is provided with a manifold 41, which functions as apartition for partitioning the interior of the casing 15 into aheat-source compartment 43 and a normal-temperature compartment 45. Theheat-source compartment 43 houses the fuel cell 9 and the fuel tank 3 soas to leave a thermal insulation space 47. The thermal insulation space47 is configured to keep the fuel cell 9 at a temperature from 60degrees C. to 80 degrees C. preferable to power generation andpreferably provided with any thermal insulation material. Thenormal-temperature compartment 45 houses the pump 7, the mixing tank 5and the printed-circuit board 13 with a control circuit and arechargeable battery 11 (11 and 13 are not shown in FIG. 4).

The manifold 41 has an opening of the air inlet port 35 at the sidethereof as shown in FIG. 5. The opening of the air inlet port 35 isprovided with a gas-liquid separation film 49, which allows penetrationof gas but prevents penetration of liquid, and a filter 51. The cathodesupply path 37 is connected to the air inlet port 35.

Moreover, the manifold 41 is provided with a suction path 53communicating with the suction port of the pump 7. The flow path 19communicating with the fuel tank 3 is connected to the suction path 53.The anode exhaust port 23 and the cathode exhaust port 25 are furtherconnected thereto.

Furthermore, the manifold 41 is provided with a discharge path 55communicating with the discharge port of the pump 7. The flow path 21communicating with the pump 7 is connected to the discharge path 55.Namely, the discharge path 55 constitutes a part of the flow path 21.The manifold 41 has threaded openings for direct fixation of the pumpand such.

Still furthermore, the manifold 41 has a passage 57 through which theanode supply path 31 interconnecting the mixing tank 5 and the fuel cell9 passes. Namely, the passage 57 constitutes a part of the anode supplypath 31.

The aforementioned constitution provides a preferable environment forpower generation by the fuel cell 9 with the methanol-water mixture andthe air. The temperature of the fuel cell 9 is kept from 60 degrees C.to 80 degrees C. preferable to the power generation because the manifold41 and thermal insulation space 47 are such configured to properlyregulate heat conduction from the fuel cell 9.

As well as thermal regulation means mentioned above, the manifold 41functions as a passageway for the various flow paths. As mentionedabove, the air inlet port 35, the suction path 53, the discharge path 55and the passage 57 pass through the manifold 41. The manifold 41collectively supports these flow paths and any other particular membersbut the manifold 41 are unnecessary for supporting the flow paths andinterconnecting the respective elements. The total constitution can beminiaturized and easily manufactured.

Namely, the manifold 41 partitions the interior of the casing 15 intothe heat-source compartment 43 and the normal-temperature compartment 45and collectively supports the flow paths, thereby the fuel cell 9 iseffectively kept at preferable temperatures and the total constitutioncan be miniaturized.

Moreover, the elements housed in the normal-temperature compartment 45are hardly influenced by heat generated by the fuel cell 9 because theinterior of the casing 15 is partitioned by the manifold 41. Thegas-liquid separation film 49 disposed at the air inlet port 35 preventsthe liquid from leaking outward when operation of the fuel cell 9 isstopped. The filter 51 disposed at the air inlet port 35 prevents dustin the air from intruding into the interior.

The aforementioned constitution can be modified into a constitutionshown in FIG. 6, in which an open-close valve 59 is disposed at the airinlet port 35, so as to prevent the liquid from leaking outward. Theopen-close valve 59 is configured to be closed when the operation of thefuel cell 9 is stopped.

The fuel tank 3 can be constituted as shown in FIG. 7 so as to steadilydischarge the fuel even how the casing 15 is oriented, in which a porousbody 61 such as a sponge is disposed along the interior wall of the fueltank 3 and an inner end of the flow path 19 abuts on or sinks into theporous body 61. The porous body 61 has capillary force so that the fuel63 therein is collected and fed to the flow path 19. The porous body 61is preferably configured to cover the whole interior wall of the fueltank 3, however, may be configured to cover limited area of the interiorwall under a condition that contact between the fuel 63 and the porousbody 61 is steadily ensured wherever the casing 15 is oriented. Forexample, the porous body 61 may be formed in an angular horseshoe shapein section and cover only three faces of the interior wall of the fueltank 3.

According to the above constitution, wherever the casing 15 is oriented,the fuel 63 therein and the porous body 61 are steadily kept in contact.Provided that a negative pressure is applied to the contact portionbetween the flow path 19 and the porous body 61, the fuel 63 is fed tothe flow path 19 by means of the capillary force of the porous body 61.Thereby the fuel tank 3 steadily discharges the fuel wherever the casing15 is oriented.

Furthermore, the mixing tank 5 can be constituted as shown in FIG. 8, inwhich a porous body 65 similar to the porous body 61 of the fuel tank 3is housed in the mixing tank 5. The porous body 65 such as a sponge isdisposed along the interior wall of the mixing tank 5 and an inner endof the anode supply path 31 abuts on or sinks into the porous body 65.The mixing tank 5 is provided with a cavity portion 67 therein. Anoutflow opening of the flow path 21 and an inflow opening of the exhaustflow path 27 face to the cavity portion 67. The outflow opening of theflow path 21 is disposed in the vicinity of the porous body 65. Anobstruction piece 69 is provided between the outflow opening of the flowpath 21 and the inflow opening of the exhaust flow path 27 so as toobstruct direct fluid transfer therebetween. In other words, a transferchannel of the fluid (gas in the case), where the fluid transfers fromthe outflow opening of the flow path 21 to the inflow opening of theexhaust flow path 27, is configured to be a detour flow path.

According to the aforementioned constitution, wherever the mixing tank 5is oriented, the mixture therein is fed to the anode supply path 31 bymeans of the capillary force of the porous body 65 in a case where anegative pressure is applied to the inner end of the anode supply path31. Thereby the mixture tank 5 steadily discharges the mixture to thefuel cell 9 and hence steady power generation can be ensured whereverthe mixture tank 5 is oriented.

Further according to the aforementioned constitution, the porous body 65directly absorbs liquid contained in the fluid, which flows into themixing tank 5 from the flow path 21 to form a gas-liquid two-phase flow,because the outflow opening of the flow path 21 is disposed in thevicinity of the porous body 65. Thereby gas-liquid separation iseffectively achieved.

Gas contained in the fluid detours around the obstruction piece 69toward the outflow opening of the exhaust flow path 27 and is henceexhausted through the exhaust flow path 27. Thereby the constitution caneffectively prevents vapor of the mixture from escaping outward so thatfuel consumption can be suppressed.

The embodiment shown in FIG. 4 can be modified as shown in FIG. 9.According to the modified embodiment, the fuel tank 3 and the mixingtank 5 are connected with each other (corresponding to the constitutionshown in FIG. 3) and the mixing tank 5 is disposed across theheat-source compartment 43 and the normal-temperature compartment 45 sothat the exhaust flow path 27 is disposed at the normal-temperaturecompartment 45. The same effect as the constitution shown in FIG. 4 canbe obtained.

The aforementioned modification can be further modified as shown in FIG.10. As compared with the constitution shown in FIG. 9, a fan 71 is addedto a motor (not shown) for driving the pump 7. By means of rotating thefan 71, external air is introduced and fed to the vicinity of theexhaust flow path 27 so that the fed air flows in the same direction asthe gas flowing in the exhaust flow path 27.

The air fed by the fan 71 cools the vicinity of the exhaust flow path 27so that the gas exhausted from the mixing tank 5 is cooled. Theconstitution reduces the vapor content of the exhaust gas and henceeffectively prevents vapor from escaping. Thereby fuel consumption canbe suppressed.

Moreover, the air fed by the fan 71 gets the exhausted gas away from thecasing 15 because these flow directions are correspondent. Thereby thevapor contained in the exhausted gas is effectively prevented fromcondensing around the exhaust flow path 27.

The manifold 41 as a partition can be modified to be a partition wall 81as shown in FIG. 11A. The partition wall 81 partitions the interior ofthe casing 15 into the heat-source compartment 43 and thenormal-temperature compartment 45, similarly to the manifold 41. Thepartition wall 81 is provided with a plurality of tubes 83 (only twotubes 83 are exemplarily shown in FIG. 11A) on one side thereof, whichconstitutes the aforementioned flow paths partly.

One partition wall 81 can be provided as shown in FIG. 11B, however, apair of partition walls 81 can be provided as shown in FIG. 11C. Thepair of partition walls 81 are disposed in parallel with each other andthe tubes 83 are put therebetween. Each of the partition walls 81 can beformed in an angular horseshoe shape in section. The tubes 83 areprevented from being disordered because the paired partition walls 81sandwich them.

The tubes 83 may be fixed by means of any fixation parts or adhesive.The tubes 83 are preferably inserted in openings or slits of thepartition wall(s) 81 as shown in FIG. 11A or 11B and hence fixed. Inthis case, the partition wall(s) 81 function as partly a partition andpartly a fixation member, and therefore any other fixation member can beomitted.

Although the invention has been described above by reference to certainembodiments of the invention, the invention is not limited to theembodiments described above. Modifications and variations of theembodiments described above will occur to those skilled in the art, inlight of the above teachings.

1. A fuel cell unit comprising: a fuel cell for electric powergeneration, the fuel cell having a cathode and an anode; a mixing tankhousing a mixture of fuel and exhaust from the fuel cell and beingconnected to the fuel cell, the mixing tank including a porous bodydisposed along an interior wall of the mixing tank, a cavity portion, aninflow path connecting the fuel cell to the cavity portion, and anoutflow path connecting the cavity portion to an outside of the mixingtank; a fuel tank housing fuel and connected to the mixing tank; and apump delivering the mixture and air to the fuel cell.
 2. The fuel cellunit of claim 1, wherein the cavity portion comprises an obstructionpiece configured to obstruct direct fluid transfer from the inflow pathto the exhaust flow path.
 3. The fuel cell unit of claim 1, furthercomprising: an exhaust flow path connecting the fuel cell to the pump.4. The fuel cell unit of claim 3, wherein the fuel tank is connected tothe exhaust flow path or the outflow path.
 5. The fuel cell unit ofclaim 1, further comprising: a casing housing the fuel cell, the pumpand at least one of the fuel tank or the mixing tank; and a partitionpartitioning an interior of the casing into a first compartment housingthe fuel cell and a second compartment.
 6. The fuel cell unit of claim5, wherein: the partition comprises a manifold including the inflow pathand the outflow path.
 7. A fuel cell unit comprising: a fuel cell forelectric power generation, the fuel cell having a cathode and an anode;a mixing tank housing a mixture of fuel and exhaust from the fuel celland being connected to the fuel cell; a fuel tank housing fuel andincluding a porous body disposed along an interior wall of the fuel tankand a flow path connecting the porous body to the mixing tank; and apump delivering the mixture and air to the fuel cell.
 8. The fuel cellunit of claim 7, further comprising: a first flow path connecting themixing tank to the fuel cell; a second flow path connecting the fuelcell to the pump; and a third flow path connecting the pump to themixing tank.
 9. The fuel cell unit of claim 8, wherein the fuel tank isconnected to the first flow path or the second flow path.
 10. The fuelcell unit of claim 7, further comprising: a casing housing the fuelcell, the pump and at least one of the fuel tank or the mixing tank; anda partition partitioning an interior of the casing into a firstcompartment housing the fuel cell and a second compartment.
 11. The fuelcell unit of claim 10, wherein: the partition comprises a manifoldincluding the first, second and third flow paths.
 12. A fuel cell unitcomprising: a fuel cell for electric power generation, the fuel cellhaving a cathode and an anode; a mixing tank housing a mixture of fueland exhaust from the fuel cell and being connected to the fuel cell; afuel tank housing fuel and connected to the mixing tank; and a pumphaving a suction port and a discharge port, the suction port beingconnected to both the fuel cell and the fuel tank so as to give negativepressure to the fuel cell and the fuel tank and the discharge port beingconnected to the mixing tank, whereby the negative pressure causesdelivery of the fuel from the fuel tank to the mixing tank and deliveryof the mixture from the mixing tank to the anode and air to the cathode.13. The fuel cell unit of claim 12, further comprising: a first flowpath connecting the mixing tank to the fuel cell; a second flow pathconnecting the fuel cell to the pump; and a third flow path connectingthe pump to the mixing tank.
 14. The fuel cell unit of claim 13, whereinthe fuel tank is connected to the first flow path or the second flowpath.
 15. The fuel cell unit of claim 13, further comprising: a casinghousing the fuel cell, the pump and at least one of the fuel tank or themixing tank; and a partition partitioning an interior of the casing intoa first compartment housing the fuel cell and a second compartment. 16.The fuel cell unit of claim 15, wherein: the partition comprises amanifold including the first, second and third flow paths.